Photographic subtractive multicolor picture



April 28, 1942. J. EGGERT EI' L 2,281,273

PHOTOGRAPHIC SUBTRAC' 1IVE MUL-TICOLOR PICTURE Filed Jan. 10, 1939 POSITIVE BLUE EXTRACT POSITIVE RED EXTRACT COPYING MVATERIAL I I I Q;

III GREEN I l I RED LIGHT LIGHT 5 ill g ..I [I GREEN sENs TIvE LAYER coNTAINING DYE FOR FORMATION OF coLoRED IMAGE I UNsENsITIzED AND uNcoLoRED EMULSION WITH YELLow RED sENsITIvE LAYER coNTAINING DYE I scREENING DYE FOR FORMATION OF coLDRED IMAGE LATENT lM OFGREEN ExTRAcT I RED LIGHT I 7 LATENT IMAGEOF PDsITIvE GREEN LATENT IMAGEOF RED EXTRACT ExTRAcT BLUE EXTRACT I DEVELOPMENT FERROCYANIDE BLUE TONED SILVER IMAGE I, I I Q 1 FERROCYANIDE 'II SILVERBLEAGHING BLUETDNING OUT DYE BATH g BATH l II I l I. z I 4 J DYE IMAGES WEAKENED BLUE sILvER IMAGEsANDUNIFoRMLY I E 'MAGE DISTRIBUTED D EsFDRFoRMATIoN S'LVER 'MAGE 4 OF COLORED IMAGEs oxIDIzING BATH To REsToRE COLOR DENsITY OF BLUE IMAGE F RRDGYANIDE BLUE IMAGE FERRoGYANIDE GREEN IMAGE INvENToRs:

JOHN EGGERT AND FERROCYAN'DE WERNER SCHULTZE RED IMAGE THEIR A TORNEYS.

Patented Apr. 28, 1942 rnoroonarrnc sun'rnno'nva MULTI- coma PICTURE John Eggert, Leipzig-Goblin,

' Schnltze, Dessau, Germany, assignors,

assignments, to General Aniline 8a notation,- Delaware and Werner by mesne Film Cor- New York, N. Y., a corporation of Application January 10, 1939, Serial No. 250,162 In Germany January 11, 1938 3 Claims. (01. 95-2) Our present invention relates to the production of subtractive multi-color pictures.

There is known a method of producing subtractive color films in which a part of the layers is treated by the silver bleaching out dyestutf process while another part is finished by one of the other known subtractive processes (see British Patent No. 454,088)

In the specification of the said patent there is described a material which on one side comprises two layers having purple and yellow dyestuffs which are bleached proportionally. to the image by the silver bleaching out dyestuff process and on the other side a layer which contains no dyestuff or only a filter dyestuil' capable of being washed out in the developer and of which a silver image is later converted into a'ferrocyanide blue picture. This arrangement of layers has especial advantage when a lenticular screen bipack is used as exposure material for a three-color exposure. The front film in this case is a lenticular screen film and comprises the blue and green sensations, whereas the back fllm becomes the red sensation. It is in this instance of great advantage if the front film, in order to obtain a better resolving power, is developed to a positive by the reversal process. The back film on the other hand is preferably developed to a negative, for in the reversal development it is more difficult to avoid variations of density and these, particularly if they occur in the blue-green component image, produce unpleasant variations of color in the copy. The above mentioned multi-layer copying material is particularly well suited for such an exposure material, for it is necessary to have positives for the silver bleaching out dyestufi' layers and a negative for the layer which is to be toned with Prussian blue as the master images.

In working with this copying material thereare certain difiiculties, the avoidance of which is an object of the present invention.

If a film on which the three component pictures have been copied is first developed and fixed and then by floating only the one side is toned blue and the film is subsequently passed through the bleaching bath necessary for the silver bleaching out dyestul'f process, it is found that the Prussian blue picture has become considerably lighter so that the color tint of the whole copy has been shifted considerably towards red. This objection can be dealt with by giving another value to the copy ng light, provided the fading is uniform and there is no further change. It has been found, however, that shortly after the copy has been finished it has a quite different appearance hours.

from that which it has after some time, say 24 The Prussian blue image has then become darker and the total color tint of the copy has been shifted back towards blue. Thus the density of the Prussian blue component image after a long time becomes more and more that of the original blue tint, that is tosay before the bleaching bath was applied. Owing to this phenomenon it is impossible to reproduce even approximately the copy once obtained. Assistance may be afforded if, after the blue toning, the film is dried and the blue toned layer is coated with a waterproof varnish, and after further drying the film is passed through ableaching bath. However, this method is very tedious.

It is a further object of our invention to provide a method which overcomes completely the trouble in question by treating the film after the bleaching out process with a strongly oxidizing agent.

Yet another object of the invention is the provision of a treatment with a bichromate-sulfuric acid bath. By means of this bath the original color densityof the ferrocyanideblue image is restored. At .the' same time the gradually increasing darkening of the blue image referred to above does not occur and copies capable of reproduction are obtained.

Other objects and advantages of our present invention will be apparent from the following disclosure.

The invention involvesa considerable simplification of the whole working in that simultaneously with this use of the bichromate-sulfuric acid bath the silver remaining from the silver bleaching out dyestuffotherwise would be effected by a milder oxidizing agent, for instance with a Farmer's reducer or copper chloride followed by fixing. With a normal silver bleaching out dye process with three dyestufis to be bleached it is not possible to use bichromate-sulfurlc acid for'removal of the silver, since the most commonlyused blue-green dyestuifs are wholly or partially destroyed. On the other hand, ithas been found most unexpectedly that the usual purple and yellow dyestuffs are stable to the bichromate-sulfuric acid bath.

The invention is further illustrated by the following example when taken with the accompanying drawing which shows diagrammatically in the form of a fiow sheet the procedln'al steps of the process involved.

On one side of a film two layers are cast, the lower being of purple color and sensitized to red while the upper is of yellow color and sensitized process is removed, which to green. In the lower layer the image is copied by red light'irom the green sensation developed to a positive while in the upper layer the image is copied by green light from the blue sensation developed to a positive; the layer on the other side of the film is not sensitized and comprises only a yellow screen dyestufi capable of being washed out by the developer. In this single-layer is copied by blue light a red sensation developed to a negative. The film is then developed and fixed, toned in blue on the side carrying the red sensation byfloating in one of the known blue toning baths, fixed and subsequently bleached by a usual silver bleaching out dye bath. The film is then run through a bath having the following composition:

Water liter 1 Potassium bichromate -grams Concentrated sulfuric acid cc l0 whereafter it is either merely washed or, in case any halogen was. present in the bleaching bath, it is again fixed for removing any silver halide in the layer and then washed and dried.

We claim:

1. In a process for producing subtractive multicolor pictures by photographicallycopyl s color sensations of a picture on to a photographic niultl-layer material comprising at least one silver halide emulsion layer colored with a dye used for the production of the finished picture by the silver bleaching out dye method and one uncolored silver halide emulsion layer, the improvement which consists in copyin the images from the corresponding color sensations into the colored and uncolored layers, developing and fixing the exposed material, forming a ferrocyanide blue image in said uncolored layer by blue toning and fixing said layer, treating the material in a silver bleaching out dye bath which alters the color of said i'errocyanide blue image and then in a bath containing an oxidizing agent which restores the original color density. of said ferrocyanide blue image, and washing (and drying the material.

2. In a process for producing subtractive multicolor pictures by photographically copying color sensations of a picture on to a photographic multi-layer material comprising at least one silver halide emulsion layer colored with a dye used for the production of the finished picture by the silver bleaching out dye method and one uncolored silver halide e ulsion layer, the improvement which consists in copylns the images fro'mgthe corresponding color sensations into the colored and uncolored layers, developing and fixing the exposed material, forming a Ierrocyanide blue image in said uncolored layer by blue toning and fixing said layer, treating the material in a silver bleaching out dye bath which alters the color of said ierrocyanide blue image and then in'a bath containing an oxidizing mixture of a bichromate and an acid which restores the original color density of said ierrocyanide blue image, and washing and drying the material.

3. In a process for producing subtractive multicolor pictures by photographically copying color sensations of a picture on to a photographic muiti-layer' material comprising a support carvrying on one side two silver halide emulsion dyed yellow and layers, the emulsion layer next to said support being dyed purple and sensitized for red, the emulsion layer remote from said support being sensitized for green, the purple and yellow dyestuffs being adapted to serve for the production of the finished picture by the silver bleaching out dye method, and carrying on the other side one silver halide emulsion layer undyed and not specially sensitized, the improvement which consists in copying the images from the green sensation developed to a positive into said purple layer by red light and from the blue sensation developed to a positive into said yellow layer by green light and from the red sensation developed to a negative into said uncolored layer by blue light, developing and fixing the exposed material, forming a ierrocyanide blue image in said uncolored layer by blue toning and fixing said layer, treating the material in a silver bleaching out dye bath which alters the color of said ierrocyanide blue image and then in a bath containing an oxidizing mixture of a bichromate and an acid which restores the original color density of said ferrocyanide blue image, and washing and drying the material.

. Jorm EGGERT.

wnRNER SCHULTZE. 

